1. Technical Field
The present disclosure relates to an optical waveguide directional coupler and a method for making the optical waveguide directional coupler.
2. Description of Related Art
Optical waveguide directional couplers are used to couple light beams of different wavelengths into an optical fiber and divide light from the optical fiber into light beams of different wavelengths.
An optical waveguide directional coupler of related art includes a base and a Y-shaped planar optical waveguide. The base includes a planar member and a Y-shaped ridge member perpendicularly formed on the planar member using an etching process. The Y-shaped planar optical waveguide is formed in the Y-shaped ridge member and exposed at an upper surface of the Y-shaped ridge member.
In order to reduce light loss, the Y-shaped planar optical waveguide controls an included angle of ends of “Y” to within about 1 degree. That is, the Y-shaped ridge member also has to have an included angle of ends of “Y” to within about 1 degree. However, it is difficult to make the included angle to within about 1 degree of the Y-shaped ridge member by the etching process because the Y-shaped ridge member is always thick, such as 3-4 μm. This promotes various product defects, such as a split product or a product with an unwanted angle.
Therefore, it is desirable to provide an optical waveguide directional coupler and a method for making same, which can overcome or alleviate the above-mention problems.